1. Field of the Invention
The present invention relates to a corrosion resistance test process for an article formed of a metal material and a coating formed on the metal material.
2. Description of Related Art
A cathode peeling-off test process is conventionally known as a test process for examining the adhesion force of a coating in an article of the above-described type (for example, see Japanese Patent Application Laid-open No.7-195612). In this test process, a procedure is employed which comprises the steps of immersing an article having a damaged portion reaching the metal material into an aqueous solution of NaCl as an electrolytic solution and then allowing a DC current to flow between the metal material having a negative polarity and an electrode placed in the aqueous solution of NaCl.
During supplying of the current, in the metal material having a negative polarity a nascent OH ion produced by the electrolysis of water reduces the force of adhesion of the coating to the metal material, starting from the damaged portion of the coating, and an H.sub.2 gas simultaneously generated peels off the coating by a physical action thereof.
In this way, the cathode peeling-off test process has an advantage that the relative excellence of the adhesion force of the coating can be determined simply, but the corrosion of the metal material attendant on the peeling-off of the coating cannot be predicted. Therefore, the cathode peeling-off test process suffers from a problem that the synthetic estimation of corrosion resistance cannot be performed for the article.
Therefore, a cycle corrosion test (CCT) has been employed which is capable of estimating both the peeling-off of the coating and the corrosion (the anode oxidation) of the metal material. This cycle corrosion test (CCT) suffers from a problem that test results cannot be obtained quickly, because a lot of test time is required to complete the test.